To me, there were more drawbacks than positives to the concept. They require two separate amplification systems (one for bass, and an amp for guitar), two cords (or a clever stereo setup) to sound good.

I thought it was novel for live playing, but rather useless for recording.

Not only is it a real iconic attention getter onstage, it's great when I am working at home laying down tracks on my computer, I can put bass, drums and guitar on a track without having to get out of my chair